Thursday, December 14, 2017

Recent race bike design is starting to acknowledge that stiffness everywhere in a bike isn't necessarily a good thing.

Riding Gravel just posted a great new article about how vibration isn't your best friend on gravel rides. I've been saying similar things for years. In fact, the article's author, in an e-mail to me, reminded me of how I have advocated against the use of cyclo cross bikes for gravel riding and have gotten into some "discussions" with others about this. This because I have often said that these bikes are too stiff and don't have the ideal geometry for gravel riding.

Those bikes specifically designed for that niche of riding have peculiar traits which have been honed over decades of design and with material technologies available now, they are typically very stiff bikes. They should be. Cyclo cross is a short event which demands racers have every iota of energy come out as power to the ground. Stiffness to the detriment of comfort is something which is a given in this sport of cyclo cross, which, let's be honest, is about suffering on many levels.

Anyway, the point is that cyclo cross bikes are not tuned to absorb the sort of vibrations that gravel road riding induces. This makes them not the best tool for the job. NOTE- I did not say that you should never use a CX bike for gravel. I merely am saying that these sharply defined bikes for a singular purpose are not really "gravel bikes". And I haven't even mentioned their geometry, which also isn't ideal.

But that isn't a big deal anymore, like it was five or more years ago. Now you can buy a bicycle tuned for gravel travel from many brands, and some of those actually address the problem of vibration by allowing flex.

Salsa Cycles Warbird was designed to absorb vibrations over gravel roads.

The Warbird specifically is allowed to have flex in the seat stays to allow the rider to have a less jarring ride. Bicycles like Trek's Domane, (which has technology which will be applied to a new model specifically for gravel, due in March), and Specialized's Roubaix models have existed for some time now, both which allow for flex that absorbs vibrations which otherwise would impede the rider's performance.

Obviously, stiffness isn't always the over-arching goal of design, but typically we see riders responding to claims of stiffness in a frame as being "good". Not just in terms of bottom bracket stiffness, or lateral stiffness, but in the entire frame. Customers think this is "good" in a frame, and they can feel this stiffness, so it must be "good".

Carbon frames have also made a name for themselves by being brutishly stiff, yet having the oft misused descriptor of "carbon absorbs vibrations" attached to them by unwitting salespeople and general riders. This may have been the case 25 years ago when carbon fiber frames were not as well made, (read: having more bonding component compared to actual carbon material), but that is not the case anymore. Carbon stiffness is incredible now days, and vibrations are not muted by the material. It just passes through frequencies and energy differently than metal frames, but the energy is still getting through to the rider.

One place where carbon has made ride quality worse than ever is in the area of forks.

Vibrations which are passed through to a rider make that rider fatigued and slower. Especially if the road surface is rough, as it is with gravel road riding. This is one of the reasons why Pro riders are gravitating to wider rims and tires. Those tires on wider rims allow for slightly lower pressures and help absorb these unwanted vibrations. No longer should you listen to that guy you know from RAGBRAI who says you should run 23mm tires at 110psi. He's wrong about that. Dead wrong.

One of my pet peeves is the use of carbon forks with massive, thick legs, tapered steer tubes, and thick "uni-crown" style fork crowns. These forks do not give an inch. (Again- riders can feel stiffness and think it means "I'm faster", but they aren't) These unforgiving forks may make sense to a cyclo cross racer, where high load cornering is almost always a thing. But for the general public, and especially for gravel riders, it is a useless commodity. Forks which flex and give are far more road worthy and comfortable. Straight steer tubes, while seemingly archaic, actually allow some flex which also helps keep the front triangle, and especially the handle bars, "quieter". Less vibration means more comfort and a faster ride. Think about this. Why would Specialized and Trek work so hard to design flex into the front ends of their bikes?

But flex, and the resulting smoother and more efficient ride quality, is a hard sell. Riders feel smoothness as "slowness". This was true back when suspension forks came along for mountain biking in the early 1990's. Riders tried it and hated it, saying the devices made them slower and sluggish. However; when running similar courses back to back with suspended and non-suspended bikes, it became clear that the smoother riding suspension equipped bikes were making for faster times. All that despite these bikes being heavier and "less stiff" than their non-suspended counterparts. Well, we know what happened next......

Why is it so hard for us to understand that flex, be it passive or active, as in suspension applications, make us faster and obviously more comfortable when almost any other human carrying vehicle employs suspension and flex? Vibrations are bad, most often, and as cyclists, we should be very wary of any bicycle company claiming that more stiffness is a good thing.

14 comments:

I'm always amazed when I see a beautiful custom steel frame with an off the shelf carpet fiber fork hanging off the front. Although in defence of the builder it's probably what the customer asked for. I will say this IMO if the builder can't make a supple steel fork he's not yet worthy of the title "frame builder". I wonder how often the carbon fork is just a cop out for lack of skill. It's sort of like going to a 5 star banquet and finding a bucket of KFC on the end of the table.

@bnelson- The snarky answer is: Anything that has more compliance! But seriously, I think you are asking me what brand/type of fork would be better. I have ridden the TRP carbon fork which shows that carbon forks can be somewhat smooth. Then there is the case of the On One Carbon fat bike fork.....

That fork looks massive and unforgiving, yet it is one of the smoothest riding forks I've had the pleasure of riding. The fork tips can actually be seen moving back and forth over the trail, and I suspect that the straight 1 1/8th steer tube has an effect on the ride quality as well.

All this to say that carbon fiber's "tunable nature" can and should be employed to make our gravel bikes smoother. The trouble is, almost all of these forks are made to be exactly the opposite since their lay-ups and designs come from CX or the road bike worlds.

Then, of course, you could always just have a steel fork made or simply purchase one that is suitable for your bike. Nearly all steel forks are much smoother than their carbon counterparts are. But, the also are heavier.

It also seems like brake selection has an effect on stiffness. Moving the braking forces closer to the wheel hub and tip of the fork on one side means that it has to be at least stiff enough to counteract that lateral twisting. Getting the brakes off the seat stays helps in the rear, but up front it’s different. It’s anecdotal, but the steel forks on my rim-brake Road, touring, and old mountain bikes “seem” to flex more and offer a much more compliant ride than my disc-brake touring and mountain bikes with steel forks. But those rim brake forks are beautiful “curved” steel forks, which seem to be shaped to allow the tips to easily move up and down a bit more than those straight leg forks. I always wondered if straight fork legs transmit shock and vibration directly up the fork leg and steerer tube. It sure seems like it. But I totally agree with what GT mentions about larger tires and lower pressure. That helps with the vibration and ride quality, especially in this present era of wide, supple, durable tires. So different than just a few years ago! By the way, there is one outlier for me: the only straight steel fork I have that seems compliant is on my Gen 1 Fargo, which continues to defy my logic and assumptions that straight steel disc brake forks can’t be supple. Go figure.

I agree that it all depends on the fork, regardless of material. I had a Spot CX carbon fork on my Vaya and it was much more compliant than the stock steel.

My current bike is an Otso Warakin with the above pictured Lithic fork. I couldn't tell the difference between the original gray one and the Lithic, but that's because I get my compliance from 48mm tires.

People say aluminum is hard and harsh, but if you can crush a pop can it's obvious that it's compliance is dependant on construction.

New carbon road bikes are pretty amazing. I went from a Smartweld Allez build to a 2018 Giant TCR. Using the same wheel set between the two bikes, he TCR almost disappears under me when riding. Then you get out of the saddle and honk the bars and the bike ROCKETS forward. Truly amazing what they can and are doing with carbon race bikes nowadays. Hell I think my TCR is more comfy than my previous Masi Gran Criterium.

On the other hand, my carbon cross bike is most definitely NOT comfy on gravel.

I think its funny that you advocate for "stiffness in the detriment of comfort" in one aspect of bike racing (cross), but not in another aspect of bike racing, gravel. Cyclocross courses are often waaaaaay rougher than a lot of the gravel roads Ive ridden and could benefit even more from suspension than gravel bikes.

When the race within the race happens in a gravel races, (attack, sprint, bridging up, etc) I 100% want "every iota of energy come out as power to the ground", just like I would want in a road race, just like in a cross race, and just like in a mountain bike race, so pretty much any bike race. There is a reason that fabian cancellaras trek domane frame was the stiffest road frame Trek made, STIFFER than Treks madone and Emonda, even though they had to ADD weight to make it stiffer. (not to mention the aggressive road bike geometry of his domane compared to the domane you have in your photo for this posting but thats a different debate) https://www.bicycling.com/bikes-gear/reviews/first-look-trek-domane-slr

All that said, I agree with you that the large majority of people riding gravel and touring gravel races (ie, riding a steady state...not doing sharp accelerations) don't need a stiff bike and comfort should trump all, why the heck not? Plus, the longer you take to finish a a ride or event, the more important comfort matters. I think if you live in an area that only has super nasty gravel roads, a full suspension MTB is honestly better than any gimmick gravel bike, especially now that the efficiency of suspension and weight of high end full suspension MTB is getting in the low 20 lbs range, similar weight to a lot of mid level gravel bikes.

thankfully we can all get what we want these days from stiff AF to limp wet noodle, its seriously crazy how niche bikes have become.

@Kelly&Ted: Hmm.... Trek's Ben Coates doesn't seem to agree with you about the Domane. Here's a quote pulled from a recent article he was interviewed for dealing with frame stiffness: "‘The Domane tuning range starts at roughly the same level of vertical compliance as the Madone [Trek’s aero race rig] and goes up to 35% more compliant without affecting pedalling stiffness,’ says Coates."

Stiffness isn't all bad. You failed to say why the engineers design for stiffness: Designing a stiff frame means that energy applied to the pedals (minus the energy lost working the mechanism of the bike and wind resistance) gets effectively converted into forward movement (as opposed to using that same energy to flex the frame--or not propel the bike forward).

This is especially the delema that full suspension MTB designers have been trying to solve---How does one design a bike that both absorbs energy (bumps, road vibration) AND efficiently converts/transfers the very limited energy provided by the rider into forward motion?

@bnelson- It's been done. Typically it is deemed to be too noodly for use in forks at competitive weights. They are expensive as well. To engineer a Ti fork to be stiff it requires so much material that they end up being about as heavy as a steel fork. Therefore it isn't really worth doing from that standpoint when steel, aluminum, and carbon can be done for less and weigh the same or less.